Electrophotographic developing apparatus



March 3, 1964 K. JONS ELECTROPHOTOGRAPHIC DEVELOPING APPARATUS Filed April 21. 1961 FIG. I

INVENTOR KURT JONS United States Patent 3,123,501 I I ELECTRUPHGTOGRAEHTC DEVELGllNG APPARATUS Kurt Jens, Wieshaden-Biehrich, Germany, assignor, by rnesne assignments, to Azoplate Corporation, Murray Hill, Nail, a corporation of New Eersey Filed Apr. 21, 1961, Ser. No. 104,709 Claims priority, application Germany Apr. 26, 1960 3 Claims. (Cl, 113429) The invention relates to a device for the development of latent electrostatic images on cut electrophotographic material.

It is known to develop latent electrostatic images by contact with a developer in powder form; the developer normally consists of a mixture of what is known as a carrier and a toner. As the carrier, glass balls of a diameter of a few hundred microns or iron filings may be used. The toners normally consist of a resin powder of a diameter of a few microns. For the application of the electrophotographic developer, mechanical devices have been used which scatter the developer on the electrophotographic layer; this has the disadvantage that uniform distribution of the toner is very difiicult with such devices unless the material is scattered very thickly to start with. In such case, however, a very large quantity of the toner must be removed and afterwards collected which results in an undesirable whirling about of the toner and, hence, loss thereof coupled with dirtying of the vicinity of the developing apparatus.

Electrophotographic developers have been placed in rotating drums having an aperture corresponding to the size of the electrophotographic material. The electrophotographic material is then stretched over this aperture by means of a clamping frame and the container is simultaneously tightly closed. An arrangement of this sort is relatively time-consuming in operation, as the clamping of the sheet is somewhat complicated and, moreover, must be done in a dark room. The development of electrophotographic material having a latent electrostatic image has also been attempted by a process in which the electrophotographic material is caused to pass through an accumulation of developer powder. In this case, however, the movement of the electrophotographic material becomes very diificult and requires special guide members. It is therefore imperative that the electrophotographic material be larger than the master being copied if these guide members are to be used Without damage to the image.

A developing device for latent electrostatic images has now been found which includes a trough with smooth side walls, an inlet slope with an angle of about 30, an adjoining curved section with a radius that is at least 500 times the thickness of the electrophotographic material being developed, an adjoining upward slope with an angle of approximately 45, which is preferably interrupted by a shoulder preferably at about the same height as the inlet, an upward discharge slope of about 60 adjoining the shoulder, and, preferably, a tank in which the developing device is disposed.

Referring to the accompanying drawings, FIG. 1 shows a cross section of one embodiment of the device of the present invention. FIG. 2 shows a perspective view of the same embodiment of the device. The developing device consists of a trough the curved surface of which has a radius 1 that is at least approximately 500 times the thickness of the cut electrophotographic material to be developed. It has been found that the radius of this curve must bear a specific relationship to the electrophotographic material being processed so that, under the weight of the developer, the sheet fits the radius of the "ice curve. With electrophotographic material of the usual thickness of 0.1 to 0.15 min, a radius of -100 mm. will be necessary. The inlet 2 to the trough should slope at about 30 to the horizontal and the discharge 3 at about 45. At about the same height as the inlet there is advantageously a shoulder 4 which interrupts the discharge. On the other side of the shoulder the upward discharge slope 5 is advantageously at an angle of about 60 to the horizontal.

For the development using the device of the invention, the electrophotographic material, e.g., an electrophotographic printing plate which has an electrophotographic coating on an aluminum support, is placed With its leading edge on the inlet slope of the trough, which is about one third to half filled with developer, and then the material is pushed under the developer. Because of its rigidity, the electrophotographic material fits the radius of curvature of the trough so well that practically the entire quantity of developer is on top of the electrophotographic material and runs or slides over the coated side. Thus, the entire coating comes into contact with the toner very uniformly without any whirling about of the developer and the latent image becomes visible.

It has proved particularly advantageous for the shoulder 4 to be incorporated in the discharge; this prevents developer being pushed out of the trough by the electro photographic material or by the mounting holes fitted therein. Such portions of developer then collect on the shoulder and can be easily tipped back into the developing device.

When the electrophotographic material has been pushed through the developing device far enough to project over the discharge end of the trough it is grasped by the other hand of the operator and pulled through the developing device. Advantageously, the device is set up in a tray or tank 6 so that any additional particles of toner that may fall from the sheet will be collected. A lid 7 serves as cover for the device when it is not in use. The device of the invention enables electrophotographic material, particularly in cut sheets, to be developed in a very simple manner to produce images having excellent uniformity.

It will be obvious to those skilled in the art that many modification may be made within the scope of the present invention without departing from the spirit thereof, and the invention includes all such modifications.

What is claimed is:

1. A device for developing latent electrophotographic images comprising a trough having a downward inlet slope of an angle of about 30", an adjoining curved portion having a radius of at least about 500 times the thickness of electrophotographic material to be developed, an adjoining upward discharge slope having an angle of about 45, and an upward outlet slope having an angle of about 60.

2. A device according to claim 1 in which the discharge slope is interrupted by a shoulder.

33. A device according to claim 2 in which the shoulder is about the same height as the inlet.

References Cited in the file of this patent UNITED STATES PATENTS 2,508,886 Morse May 23, 1950 2,972,331 Limberger Feb. 21, 1961 3,021,817 Limberger Feb. 20, 1962 FOREIGN PATENTS 446,215 France Sept. 26, 1912 1,114,965 France Dec. 26, 1955 1,196,529 France May 25, 1959 

1. A DEVICE FOR DEVELOPING LATENT ELECTROPHOTOGRAPHIC IMAGES COMPRISING A TROUGH HAVING A DOWNWARD INLET SLOPE OF AN ANGLE OF ABOUT 30* AND ADJOINING CURVED PORTION HAVING A RADIUS OF AT LEAST ABOUT 500 TIMES THE THICKNESS OF ELECTROGRAPHIC MATERIAL TO BE DEVELOPED, AN ADJOINING UPWARD DISCHARGE SLOPE HAVING AN ANGLE OF 